This invention relates generally to neutral bar assemblies made up of several neutral bars electrically and mechanically coupled together and the method of making such neutral bar assemblies.
Electrical enclosures, such as breaker boxes, commonly have only one neutral bar mounted therein for the purpose of referencing and/or grounding distribution circuits. In recent times, the use of electronic devices has expanded significantly, both commercially and in our homes. Consequently, the number of neutral or grounding outlets necessary to accommodate these additional electronic devices has increased. One solution to this problem is to expand or increase the size of the electrical enclosure to accommodate additional neutral bars. Customers such as home owners resist this solution because either: 1) it is too costly or 2) there is insufficient space for a larger electrical enclosure. Consequently, there is a need to add additional neutral or grounding outlets in an electrical enclosure of a fixed size.
Previous attempts to electrically couple multiple neutral bars together efficiently in a fixed space or volume have included mounting multiple neutral bars on a stepped bracket, such as is disclosed in U.S. Pat. No. 2,909,757. This method of mounting multiple neutral bars requires additional screws and mounting brackets and is therefore costly. In addition, the limited space within an electrical enclosure may not allow an electrician or an original equipment manufacture (OEM) to add additional neutral bars in this manner. Furthermore, the spacing between adjacent neutral bars in such an assembly may be insufficient so that an electrician may be unable to see into which hole he or she is inserting a wire.
Another drawback with existing neutral bar assemblies is that in order for the neutral bars to receive neutral conductors or wires of different diameters, additional equipment is required. U.S. Pat. No. 3,594,710 discloses such a neutral bar assembly which requires nuts and bolts to secure neutral bars having different hole spacings and different wire range holes together in an assembly. Again, this method of mounting neutral bars together is costly because of the additional equipment required.
The most common current method of securing additional neutral bars to a mounted neutral bar in an electrical enclosure is to independently mount each additional neutral bar in the electrical enclosure and connect the bars with a single wire. This method is costly and provides only a single electrical connection between the neutral bars.
Another less common method of electrically joining neutral bars in an electrical enclosure has been to bend a copper wire into a Z shape and secure the ends of the copper wire in wire-receiving holes of the neutral bars with wire binding screws. However, this method does not allow the neutral bars to be placed close enough together to maximize the space inside the electrical enclosure. In addition, this method is not practical because the neutral bars are not rigidly mounted together. Therefore, when an electrician tightens a wire binding screw to secure a wire into one of the openings in one of the neutral bars, the z-shaped copper wire may bend or deflect, jeopardizing the electrical connection between the neutral bars.
Consequently, there is a need to electrically and structurally connect several neutral bars together in a compact, efficient, and cost-effective manner, without increasing the size of the electrical enclosure. There is also a need for a method of connecting adjacent neutral bars structurally and electrically such that the wire-binding screws may be torqued properly without disturbing the electrical connection and spacing between the neutral bars. Further, there is a need for a neutral bar assembly through which an electrician may see to put the correct wire in the correct hole or bore. There is also a need for a method of structurally and electrically joining adjacent neutral bars having different hole spacings and different wire range holes. Finally, there is a need for a relatively inexpensive and convenient method to use expanders for structurally and electrically interconnecting two or more neutral bars together to form a spatially compact multi-bar assembly.
The present invention overcomes the foregoing and other shortcomings and drawbacks of neutral bar expanders and assemblies heretofore known. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the present invention.
The present invention comprises a neutral bar assembly in which at least two neutral bars are electrically and mechanically secured together with a pair of expanders to form a spatially compact multi-bar assembly. In one preferred embodiment of the present invention, first and second neutral bars are coupled together with a pair of generally U-shaped expanders, each having spaced-apart, generally parallel legs which are received in respective wire-receiving bores of the two neutral bars being assembled to each other. In an alternative preferred embodiment of the present invention, three neutral bars are electrically and mechanically joined together with a pair of expanders, which are each generally shaped like a staircase, each having three spaced-apart, generally parallel legs which are received in respective wire-receiving bores of the neutral bars being assembled to each other. Although the expanders of the present invention preferably secure together two or three neutral bars, any number of neutral bars may be joined together in accordance with the present invention.
In each of the preferred embodiments of the present invention, the neutral bars are preferably die cast of aluminum, as is conventional; however, the neutral bars may be made of any electrically conductive material and stamped or extruded. Each of the neutral bars is generally elongated in overall shape with a rectangular transverse cross-section, having generally planar, parallel front and rear surfaces, generally planar, parallel top and bottom surfaces, and generally planar, parallel end surfaces.
A plurality of spaced bores extend through the neutral bar from the front surface to the rear surface. These bores are typically not threaded, although they may be threaded. The bores are sized and adapted to receive grounding wires from the rear thereof, as is conventional. The bores within each of the neutral bars are typically the same diameter and have a defined pitch, i.e. the distance between the centers of adjacent bores. The neutral bars are generally less than a foot long, however, may be three or four feet long depending upon the size of the breaker box or electrical enclosure which contains them. One common size bore for a neutral bar is approximately a quarter inch in diameter, accommodating wire gauges from 14 to 4, increasing in wire diameter. In addition, the bores may be of a larger diameter as to accommodate larger gauge wires, e.g. 2 to 0 gauge wires. One of the advantages of the present invention is that neutral bars made from different manufacturers, having different pitches may be joined together. In addition, neutral bars having different lengths and bores of different diameters may be joined together in accordance with the present invention.
In order to secure the wires inside the bores, a plurality of spaced, threaded holes extend downwardly from the top surface of the neutral bar into the bores of the neutral bar. A plurality of wire-binding screws are engaged in the threaded holes and when rotated advance into the bores of the neutral bar, thereby trapping or securing the grounding wires between the bores and the bottoms of the wire-binding screws.
Each of the expanders of the present invention is a unitary member made from an electrically conductive material. The expanders are preferably made of aluminum, but may be made of bronze, copper, or any other conductive material. Each of the expanders is preferably cast from aluminum, but may be manufactured via other methods, such as welding multiple pieces together. In addition, the expanders may be made by extruding a length of electrically conductive material such as aluminum in the desired shape and then cutting that extruded length in a transverse direction so that each expander has a desired width.
Each of the expanders has a body portion and at least two legs extending forwardly from the body portion. In one preferred embodiment of the present invention, each expander is generally U-shaped, having two spaced, parallel legs extending forwardly from a body portion. In another preferred embodiment of the present invention used to connect three or more neutral bars, each of the expanders is generally staircase-shaped, having three spaced, parallel legs extending forwardly from a body portion. In accordance with the present invention, the expanders may assume other configurations and shapes, as will be described in more detail below.
In each of the embodiments of the present invention, the legs of the expanders are inserted into the bores of the neutral bars and the wire-binding screws tightened in order to secure the legs of the expanders in the bores of the neutral bars. No additional brackets, bolts or hardware is necessary to secure the expanders to the neutral bars.
One method of making the neutral bar assembly of the present invention comprises adding at least one neutral bar to a neutral bar already mounted in an electrical enclosure. In this method, one of the legs of each of the expanders is inserted into one of the bores of each neutral bar to be added. Then the remaining legs of each of the expanders are inserted into the bores of the already mounted neutral bar and secured therein by tightening the appropriate wire-binding screws. Another method of making the neutral bar assembly of the present invention is the join all the neutral bars together into an assembly before the assembly is mounted in the electrical enclosure.